This invention relates to a pneumatic tire which improves driving comfort without lowering driving performance such as maneuvering stability.
Characteristics required for recent pneumatic tires are not only driving performance such as maneuvering stability but also higher driving comfort. Driving comfort of tires is typified by an impact value of vibration carried into a car from a road surface through the tires and by a magnitude of noises, and this vibration is transmitted into the car through a transmission route ranging from the tread of each tire, its outer and inner side walls, its outer and inner beads and a rim and disc.
To improve driving comfort, it has been customary to reduce block rigidity of the tread so as to reduce righting moment of external force given from the road surface.
However, if block rigidity is reduced throughout the entire tread surface, there occurs the problem that driving performance such as maneuvering stability drops.
With the conversion of a wheel driving system to a front wheel driving system (FWD) and with the expansion of the internal space of a cabin in recent years, an asymmetric structure has been employed for a wheel structure so as to maximize the inner space of the wheel, and an offset quantity of a connecting position of a disc to a rim from the center of a rim width to a wheel outer side has become greater and greater. The inventors of the present invention have carried out studies on the relationship of vibration transmission between the wheel having such an asymmetric structure and a tire, and have found that there is a very close correlationship between them.
In other words, when a vibration transmission factor transmitted from both side walls of the tire to the wheel having the asymmetric structure is examined, it has been clarified that the transmission factor of vibration passing through the rim end on the offset side (wheel outer side) of the disc is greater than the transmission factor of vibration passing through the rim end on the opposite side (wheel inner side), and moreover, this tendency becomes all the more remarkable with an increasing offset distance of the connecting position of the disc from the center of the rim width.
The inventors have further examined in detail this finding in relation with maneuvering stability, and have found out that the problems of maneuvering stability and driving comfort, which are contradictory to each other, can be solved and driving comfort can be improved by skillfully utilizing this correlationship.